The aim of this proposal is to investigate the localization and role of the adhesion molecule N-cadherin at the developing synapse in the mammalian brain. Formation of pre- and postsynaptic specializations and the molecular orchestration of essential proteins for signal transduction follows contact of an axon with a target and is now known to occur in the absence of neurotransmission. It is not yet known what proteins and interactions are required for this process, but it is suspected that adhesion molecules will play a crucial role. Cadherins mediate important adhesive interactions during cellular morphogenesis, neurite outgrowth, and axonal guidance, but the importance of cadherins at the neural synapse remains unknown. The distribution and temporal expression patterns of N-cadherin implicate this adhesion molecule in synapse formation. Therefore, in this study we hope to determine more precisely the localization and timing of N-cadherin aggregation at synaptic sites and also determine if it is necessary for synapse formation. These experiments will be conducted in live rat hippocampal slices and will include a variety of techniques including immunocytochemistry, biolistic transfection of GFP and DsRed-fusion proteins, use dominant negative protein constructs, and time-lapse confocal microscopy. The studies proposed here will further our understanding of the roles of cell adhesion molecules and also elucidate mechanisms of synapse formation and maintenance in the developing mammalian brain.